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Using rsync to Synchronize Files

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Using rsync to synchronize files

The purpose of this article is to provide an understanding of using the rsync tool.

Rsync stands for "remote synchronization" and it is an efficient tool for copying and synchronizing files or directories locally or remotely. The efficiency is achieved by moving only those parts of the files that have changed, instead of copying everything again.

Usage

Syntax

The rsync syntax is really simple:

rsync [OPTIONS] SOURCE DESTINATION

Options

The following are some of the most useful options to add to the rsync command:

  • -v or --verbose: the verbose flag will display information about the progress of the task.
  • -a or --archive: equals -rlptgoD. The archive flag sets the most common options instead of setting them individually.

The following are the options set with -a that can also be set one by one:

  • -r or --recursive: recurses into directories. Must be used when you need to copy all the contents inside a directory.
  • -l or --links: copies symlinks as symlinks, does not copy the file to which they point to avoiding loopbacks to other directories.
  • -p or --perms: preserves the permission of the file.
  • -t or --times: preserves the original modification timestamps.
  • -g or --group: preserves the files' groups ownership.
  • -o or --owner: preservers the files' owners.
  • -D: preserves the device files and special files. You can use the options --devices and --specials to accomplish this.

Some other options that can be used are:

  • -progress: displays the progress status per file.
  • --max-size=SIZE: avoids transferring files larger than the specified size.
  • --min-size=SIZE: avoids transferring files smaller than the specified size.
Source and destination paths

It is important to take into consideration how the source and destination paths are specified since a slash can change the behavior.

For exmample, to copy everything inside a directory called in /home into another one called /new/destination/ the correct rsync syntax would be:

rsync -a /home/ /new/destination

To copy the directory so that a new folder called home is also created in the destination directory the syntax would be:

rsync -a /home /new/destination

Note that a single slash after /home will change the end result.

Using rsync with a remote host

When having SSH access to a remote host it is possible to use rsync with a really similar syntax. To copy the contents from the /home directory to the /home/new directory in a host called REMOTE_HOST a push operation is needed. The syntax would be:

rsync -a /home USER@REMOTE_HOST:/home/new

It is possible to retrieve files from a remote host to your local machine using rsync with a pull operation. The syntax is similar as the mentioned above but now the remote host is the source:

rsync -a USER@REMOTE_HOST:/home/new /home

Conclusions

Using the rsync tool is a reliable and efficient way to synchronize files between directories or hosts. A traditional copy command would not preserve all of the files' properties and would take a longer time since it copies everything.

With the options mentioned in this article it is possible to determine the properties that should also be copied and the rsync algorithm will reduce the task time by copying only the differences between both source and destination.

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Updated 12 months ago